When I use the Van der Pauw method to measure the resistance of V2O5, the result is not good: showing evident metal-semiconductor contact effect. The contact I used before was silver paste, since I needed it to dry and solidify so I could a attach gold wire. The contact might need to be changed.
Dear Shuyu,
As Professor Nita suggested, indium will probably do the trick. To be completely thorough, you would like to find a contact metal that has as similar work function as your material of interest to minimize the Schottky barrier you are observing. However, it often isn't critical due to something called Fermi pinning.
Hi Sebastian, I tried gold that has similar work function with V2O5, yet the result is still not that good.
I suggest the following: first run a quick 2pt I-V measurement. This can help determine the voltage range where the contact is more linear, and the right choice may improve your 4pt measurement (which, at least ideally, doesn't require excellent ohmic contacts).
I never measured this particular oxide, but I suggest trying a very thin (~2 nm) Ti layer followed by 20-40nm of Au; if you have access to an e-beam evaporator, it is rather straightforward.
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